Recovery in passenger demand is many months away, yet IndiGo, Vistara and SpiceJet have launched sales. What? Sales by airlines are similar to other businesses. Discounts pull passengers in hiding and stimulate demand. Plane seats are perishable inventory—an empty seat on a flight is lost forever. So it makes sense to sell some seats on discount (10% seats at Rs XX, 20% at Rs XX etc) and fill those. Airline revenue and inventory management is complex, but airlines typically go big on discounted fares on flights with low passenger occupancy. Of course, there are other factors such as the kind of routes and travel habits (peak season, don't expect sales) that weigh on these actions. Best to book early.